I can't remember much about this game but LOVED it.
You had to make your way through a long succession of levels, seeking treasures (and/or a key?) and avoiding various monsters/adversaries. Each level was some kind of landscape or formation. Occasionally you could go into something like a teleport that could send you to another level.
Not sure what computer I played it on but could find out. This was England, mid-1980s, and we played it on the telly IIRC.
Any help gratefully received. Thanks!